1. Thesis work seminar presentation 18.10.2005 Mari-Jaana Pelkonen 51529B
Estimating end-to-end performance in 3G Long-Term Evolution compared to HSDPA
Thesis work seminar presentation
Mari-Jaana Pelkonen 51529B

2. Acknowledgement Supervisor: Prof. Heikki Hämmäinen
Instructor: Jani Kokkonen M.Sc
Nokia Networks, System Technologies

3. Agenda Thesis introduction HSDPA overview 3G LTE overview
Estimation work
Summary

4. Thesis introduction
3G Long-Term Evolution standardization effort started in late 2004 in 3GPP
3G networks are implemented at very slow phase. One major reason for the operators low investment willingness is the low capacity it offers to the operator and to the customer.
IEEE is standardizing mobile WiMAX => Threat for loosing competitive edge.
In Japan the telecom technology is one step forward: DoCoMo is driving the standardization.
Why not 4G? 4G will be a system that connects all the existing and future networks seamlessly together. The technology is not yet ready for that. 3G LTE is a evolution step towards the 4G, enabling the operators to use the existing infrastructure longer.
Target to standardize simple, IP optimize network, offering mobile DSL type connections.

5. Thesis introduction
The scope of the thesis work was to prove that the performance in presented 3G LTE architecture is better than in the current available systems.
3G HSDPA was selected to the reference architecture.
We were not only interested whether the new system is better, but why and why not.
How much of the improvement could be achieved only improving capacity of the legacy systems?
What is the impact of the new architecture solutions
Different applications have different requirements for the network, performance is application specific. Therefore delay and throughput impact estimations were done for three applications: Web browsing, streaming video and VoIP.

6. Thesis introduction
This thesis work was written in 3G Long-Term Evolution architecture project
One part was literature study about 3G HSDPA performance and performance in general.
3G LTE specific part is taken from the architecture project and standardization contributions. The 3G LTE architecture presented in this work is DRAFT architecture. It will not be standardized as presented here.
The estimation work is done using a Service performance Excel tool created to calculate delays in 3G networks. The tool consists of signaling flows for different applications. For that work, the 3G LTE specific parts were added to the tool.
Values used in the tool are for 3G networks measured or estimated. To get 3G LTE values, I consulted several experts working with that area. Some of the values are targets, other derived from 3G values and the rest are educated guesses.

7. HSDPA
High-Speed Downlink Packet Access is 3G performance enhancement technology. It does not change the core network, but only the radio interface in the downlink direction.
HSDPA offers theoretical DL bit rates up to 14.4 Mbps.
Only test networks implemented, not yet in commercial use. The effective bit rate offered to users is assumed to be around 800 kbps.

8. HSDPA: 3G architecture UE Node B RNC SGSN GGSN UTRAN CN PS domain HLR
UE = User Equipment
Node B = base station
RNC = Radio Network Controller
RNS = Radio Network System
CN = Core Network
UTRAN = Universal Terrestrial Radio Access Network
SGSN = Service Gateway Supporting Node
GGSN = Gateway GGSN Supporting Node UE
Node B
RNC
SGSN
GGSN
UTRAN
CN PS domain
HLR
AuC
EIR
Registers CN Uu Iu
RNS
Iub Gn Gi

9. HSDPA: 3G QoS bearer architecture
End-to-end Service
Local Bearer Service
Backbone Bearer Service
CN Bearer Service
External Bearer Service
Iu Bearer Service
Radio Bearer Service
UTRA Service
Physical Bearer Service
UMTS Bearer Service
Radio Access Bearer Service TE MT
UTRAN
CN Iu edge
CN Gateway

10. HSDPA: Protocol stack (user plane)
GGSN
3G-SGSN
RNC UE
Server
HLR BS
MAC-hs
HS-DSCH FP L2 L1
Radio L1
MAC
PDCP
IPv6/v4 u
Application
TCP/UDP
RLC-U IP
UDP
GTP-U
MAC-D U
Iub
IuPs Gn Gr

11. HSDPA: WCDMA RRC and PMM states
CELL_PCH
CELL_FACH
CELL_DCH
RRC state change
DCH channel allocation time
2-5 s timer
If DL activated, paging causes delay
IDLE
PMM Detached
PMM Connected
RRC Connection establishment time
GPRS Attach
Mobile is allowed to send data in CELL_FACH and CELL_DCH states. DCH channel is dedicated channel for end user data.
CELL_PCH and URA_PCH (not shown in the figure) are used for paging.
In idle mode mobile has no radio connection.

12. 3G LTE IP optimized network architecture
Target is to solve the performance problems that current 3G architecture has and offer DSL type mobile internet connection.
Simple architecture
Short user plane RTT
Cell capacity up to 100 Mbps
In between 3G and 4G, interworking with existing and future network technologies inbuilt in the architecture.

13. 3G LTE: Goodbye circuit switched voice!
The evolution of packet switched network technology has made possible to transmit voice over IP network with acceptable end-user performance.
The SKYPE is one of the most popular example of that.
Current 3G and 2G networks are optimized for circuit switched voice, that makes them complex and not best possible for data traffic.
Operators need to invest in and maintain two parallel networks: CS and PS.
The all-IP architecture will be simple and cheap!
Of course operators are not willing to cannibalize their CS voice business by offering VoIP. The success of SKYPE shows, that former or later customers are changing to the VoIP. To ensure not to loose the future profit, operators need to be inside the VoIP business.

14. 3G LTE reference architecture
UE = User Equipment
BS = Base Station
SN-C = Serving Node (Control plane)
SN-U = Serving Node (User plane)
SGW = Service Gateway
RNC functionalities moved in the base station.
Access Network BS
Serving
Node - C U
Service
Gateway
Subscription
Operator
service
network
AAA
Registers
Internet
Inter
connection HA

15. 3G LTE: QoS bearer architectureBS SN
User - IP
Tunneling or forwarding
Transport
Radio UE
Note: this is called bearerless compared to current 3G bearer architecture. Air interface connection establishment and modification is simplified by reducing the number of air-interface bearers.
Instead of four radio bearers, only one radio bearer has to be established. This leads to the significantly reduced radio connection setup time.

16. 3G LTE: Mobility Management States
Idle
Active
Associate
RLID
Release
Detached
Connectio n
Failure
, UE
local
release
Assign
UE_LLA,
Release UE_LLA &
Connection
Rele
ase
The number of channels reduced. Only one channel for user data. That channel is associated, if UE is in Active state.
That allows to reduce the number of states to three. If user is connected to the network, it is Idle or Active, whether it has data to send or receive.

17. 3G LTE: Protocol stack (User plane)
All-IP protocol architecture, one continuous IP layer through all the network elements.

18. Estimation work
Throughputs, link utilizations and transfer delays for TCP is estimated for different file sizes.
Studied applications were VoIP, web browsing and streaming.
For VoIP call, the most critical Key Performance Identifiers are session setup delay, end-to-end delay and delay variation. Session setup delay and end-to-end delay were estimated.
For web browsing, the KPI studied is the click-to-content time, i.e. the time that takes after user selects page until it is loaded to his computer.
KPIs for streaming are session setup delay and the throughput. Because throughput is studied separately, only session setup delay is estimated.

19. Estimation work: TCP throughputs
TCP throughput for 3G LTE (800 kbps) is better with all file sizes than HSDPA
Due the TCP slow start effect, the TCP throughput is worse with small files than the large ones.

20. Estimation work: TCP Link utilizations and delays
3G LTE link utilization with same bit rate is notable better.

21. Estimation work: Streaming session setup time
Phase
3G LTE delay (ms)
HSDPA with always on PDP context (ms)
HSDPA delay (ms)
RTSP signaling
329
535
TCP connection establishment 77
156
Primary PDP context without RAB -
769
RAB establishment
1408
Secondary PDP context with RAB
1975
1974
Delay before buffering
406
4073
4843
Buffering
5000
Total
5406
9073
9843

22. Estimation work: VoIP call with Internet Multimedia Subsystem
SIP session setup delay (ms)
End-to-end delay (ms) (for 210 bytes VoIP packet)
RTT UE1-UE2-UE1 (ms)
3G LTE
2385 34 68
HSDPA with always on PDP context
7894 97
194
Difference
5509 63
126
External network delay not calculated
Both end-users are connected to their own IMSs.
For 3G LTE the SIP session setup delay is less than the circuit switch PSTN call setup delay.
The difference ín session setup delay is 5.5 second. Most of the difference is caused by the secondary PDP context activation and RAB procedures.
End-to-end delay for 3G LTE 30 ms is not notable for user. HSDPA 71 ms end-to-end delay is not notable with echo cancellation.

23. Estimation work: VoIP End-toEnd Delay
RNC
3G-SGSN
GGSN
IP/MPLS/IPoATM-backbone
Node B UE
IMS 1 3G
RNC
3G-SGSN
GGSN
IP/MPLS/IPoATM-backbone
Node B UE
IMS 2
End-to-end delay consists of processing delays in UEs and in every network node in between them and transition delays between nodes.

24. Estimation work: Web browsing
Estimation is done for HSDPA with and without always-on PDP context.
First page delay includes radio connection establishment, PDP context activation and DNS query
Second page delay consists only HTTP signaling.

25. First page delay divided into parts

26. Summary
Performance advantage of presented 3G LTE is clear for investigated applications.
The session setup delay (PDP context and radio connection establishment) in 3G affects worst in short living applications, or applications that transfers only small amount of data.
Enhanced air- interface effect is notable only with applications that transmit large files
The capacity increase or RTT decrease is not the only way to the better performance. The IP connectivity added with bearerless model presented here is needed to reduce the session setup latencies.